Projection display apparatus for suppressing speckle noise

Abstract

A projection display apparatus of the present invention can include a light source; an optical modulator, configured to repeatedly output a modulation beam N times in a predetermined time range, the modulation beam being generated by identically modulating a bema of light emitted from the light source and N being a nature number and equal to or greater than 2; a mirror, configured to reflect the modulation beam, which is repeatedly outputted N times, to scan the modulation beam to an identical point of a screen; and a polarization rotating unit, configured to rotate a polarization direction of the modulation beam for each time the modulation beam is scanned. With the present invention, the speckle noises on a video scanned to a screen can be suppressed.

1 . A projection display apparatus, comprising:
 a light source;   an optical modulator, configured to repeatedly output a modulation beam N times in a predetermined time range, the modulation beam being generated by identically modulating a bema of light emitted from the light source and N being a nature number and equal to or greater than 2;   a mirror, configured to reflect the modulation beam, which is repeatedly outputted N times, to scan the modulation beam to an identical point of a screen; and   a polarization rotating unit, configured to rotate a polarization direction of the modulation beam for each time the modulation beam is scanned.   
   
   
       2 . The apparatus of  claim 1 , wherein the predetermined time range is smaller than a time resolution of a human vision system (HVS). 
   
   
       3 . The apparatus of  claim 1 , wherein the optical modulator is a one-dimensional optical modulator that outputs a linear modulation beam, and
 the mirror is a scanning mirror that forms a two-dimensional video by scanning a linear modulation beam, repeatedly outputted N times, to the screen,   whereas the polarization rotating unit rotates a polarization direction of the linear modulation beam for each time the linear modulation beam is scanned.   
   
   
       4 . The apparatus of  claim 1 , wherein the light source comprises a red light source, a green light source, and a blue light source, and
 the red, green, and blue light sources output each beam according to a predetermined order.   
   
   
       5 . The apparatus of  claim 4 , wherein the light source outputs beams at a period of a set of beams consisting of a red beam, a green beam, and a blue beam at least once; and
 the optical modulator outputs the modulation beam by modulating the beams N times identically at the period of a set of beams,   whereas the polarization rotating unit rotates a polarization direction of the modulation beam at the period of a set of beams.   
   
   
       6 . The apparatus of  claim 5 , wherein, if the modulation beam, which is outputted by identically modulating the beams N times at the period of the set of beams, is scanned to an identical point of the screen, a full-color video frame is completely formed. 
   
   
       7 . The apparatus of  claim 5 , wherein a multiple of the N of the period of the set of beams is smaller than a period of a human time resolution. 
   
   
       8 . The apparatus of  claim 1 , wherein the polarization rotating unit is a liquid crystal polarization rotating unit. 
   
   
       9 . The apparatus of  claim 1 , wherein the polarization rotating beam is placed between the mirror and the screen.